1. Field of the Invention
The present invention relates to a tube joint for connecting, for example, a fluid tube for introducing or discharging a fluid.
2. Description of the Related Art
A tube joint has been hitherto used for fluid piping of a brake used in a vehicle such as an automobile, in order to connect fluid pipes into which a pressure fluid for driving the brake is introduced. As shown in FIG. 11, such a tube joint 1 comprises a connecting section 3 which has one end to be connected to a port 2 of a pressure fluid-operated apparatus or the like, a main body 4 which is integrally connected to the other end of the connecting section 3, and a fluid pipe 5 which is inserted into an end opposite to the connecting section 3 of the main body 4. The connecting section 3 is made of a metal material with one end screw-engaged with the port 2 and integrally fixed thereto. The other end of the connecting section 3 has substantially the constant diameter, and is inserted into the main body 4. An O-ring 6 is installed to an annular groove on the outer circumference of the other end of the connecting section 3. The air-tightness in the main body 4 and the connecting section 3 is maintained by the O-ring 6.
The port 2 of the pressure fluid-operated apparatus or the like, to which the connecting section 3 is connected, is generally formed of a metal material. When external force is applied, for example, to the fluid piping 5 and the tube joint 1, the connecting section 3 may be broken by the load applied to the connecting portion of the connecting section 3 if the connecting section 3 is formed of a resin material. Further, the screw formed on the connecting section 3 may be abraded by repeated attachment to and detachment from the port 2. Therefore, the connecting section 3 is generally to formed of a metal material in order to increase the strength.
The main body 4 is formed of a resin material in order to realize a light weight. The end of the main body 4, to which the connecting section 3 is connected, has substantially the same diameter for the outer circumference and the inner circumference.
The tube joint 1 is fixed in a state of cantilever in which only one end of the connecting section 3 is supported by the port 2. The tube joint 1 and the fluid pipe 5 used in the brake are generally provided on the floor surface of a vehicle such as an automobile so that they are opposed to a road surface.
As for the conventional tube joint 1, for example, unexpected external force (see the arrow A in FIG. 11) is sometimes applied to the fluid piping 5 of the main body 4, for example, by pebbles or gravels from the road surface. In such a situation, the main body 4 is deformed downwardly by the external force about the connecting portion between the main body 4 and the connecting section 3, because the main body 4 is formed of the resin material. However, the connecting section 3, to which the main body 4 is coupled, is not deformed because the connecting section 3 is formed of the metal material and is completely fixed to the port 2. As a result, stress is generated from the outer circumferential surface to the inner circumference of the main body 4 near the connecting portion of the main body 4 and the connecting section 3. The main body 4 may be broken near the connecting portion.